Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in one or more optical properties when stimulated to a different electronic state. Electrochromic materials, and the devices made from them, may be incorporated into, for example, windows for home, commercial, or other uses. The color, transmittance, absorbance, or reflectance of such electrochromic windows can be changed by inducing a change in the electrochromic material, for example, by applying a voltage across the electrochromic material. Such capabilities can allow for control over the intensities of various wavelengths of light that may pass through the window. For example, a first voltage applied to an electrochromic device of the window may cause the window to darken while a second voltage may cause the window to lighten.
Electrochromic devices, like most controllable optically-switchable devices, contain electrical connections for controlling the application of electrical stimulus (for example, in the form of a controlled applied voltage and/or current) to drive optical transitions and/or to maintain optical states. Electrochromic devices are frequently implemented as very thin layers that cover the face of a surface such as a window surface. Such devices typically include transparent conductors, often in the form of one or more layers that cover electrochromic electrodes and distribute applied voltage over the face of the device to effect a complete and efficient optical transmission.